Micro-miniature relay



Oc 25, 1960 P. T. MlLLUNZl MICRO-MINIATURE RELAY 2 Sheets-Sheet 1 Filed July 15, 1959 ATTORNEY Oct. 25, 1960 P. T. MlLLUNZl 2,957,965

MICRO-MINIATURE RELAY Filed July 15, 1959 2 Sheets-Sheet 2 INVENTOR. Pins? 7? fi/ZZZ/A/Z/ ATTORNEY United States Patent MICRO-MINIATURE RELAY Peter T. Millunzi, Du Quoin, Ill., assignor to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Filed July 15, 1959, Ser. No. 827,222

'13 Claims. (Cl. 200-102) This invention relates generally to switches or relays, and more particularly to micro-miniature relays.

Certain types of electrical equipment, having low current, low voltage circuits require electromagnetically actuated switches and relays of exceedingly small dimensions. However, these relays and switches continue to have difliculty in meeting the rigid shock and vibration requirements for use in existing and proposed aircrafts and missiles. One of the methods used in combatting these environments has been the use of balanced rotating armature relay construction. Although this has been an improvement, this does not permit such relays to meet the extreme requirements Without an increase in power input or size. To the present time, a relay of this type has not had the necessary efficiency from a volume or space allocation standpoint. Because of the desire to use a balanced rotary armature type relay, a three building *block principle Was used; that is a block of space was allocated specifically for contacts. This generally included a base header to which the relay contacts were permanently fastened. Another volume of space was allocated to the armature, and a third volume was allocated to the coils. Since that volume of space allocated for the armature extended to the outside walls of the relay, the space left between the armature and outer extremities of the relay Was not used and was wasted as far as the relay was concerned.

It is the intention of the present invention to provide means and methods for providing shock and vibration immunization within a relay structure so as to aid the ability of the rotary armature to Withstand these effects. In addition, the invention takes advantage of the normally unused space between the armature and the outer extremities or Walls of the relay by placing the relay contacts within this space. This permits the relay to be independent of its base terminal header, thus allowing complete flexibility as to terminal configuration of the base header without necessitating complete constructional modification.

The elimination of the need for a base header to which contacts were normally mounted, permits the use of the present relay invention as either an open, individual relay, or as a multiple relay structure capable of being sealed within a large container providing a greater density of relays for a given volume. Furthermore, since the contacts have been removed from the base, the relay no longer needs that volume of space formally allocated to the contacts, and therefore, this space may be utilized in obtaining increased coil length which permits greater sensitivity for the relay in the same overall size. Thus, the present invention makes possible improvements which are adapted to render the relay much more efficient and flexible than those priorily available.

Accordingly, the present invention affords complete independence of the relay from its associated base header; it gives complete flexibility as to the type of base header terminal configuration that can be used; it gives greater relay sensitivity at existing sizes; it gives the same sensitivity at reduced sizes; it has greater shock and vibration immunity; it is more reliable in operation and; it isolates both the contacts and the armature within a spring mounted box type construction so as to give greater protection from external shock and vibration.

It is therefore an object of the present invention to provide a micro-miniature relay of extreme sensitivity and reliability.

Another object of the present invention is to provide an improved construction for a micro-miniature relay.

Still another object of the present invention is to provide a micro-miniature relay of substantially reduced dimensions including separate contact and base headers allowing for advanced constructions of modular packages used in complex circuitry which require a multiplicity of stacked relays.

Yet another object of the present invention is the construction of a micro-miniature relay of the rotary armature type obviating the need for cumbersome biasing elements and wherein spatial dimensions are reduced by conserving areas formerly unused.

Still another object of the present invention i to provide a micro-miniature, balanced, rotary armature relay in which the coil windings used therein are increased with consequent increase in sensitivity and etficiency.

Yet another object of the present invention is to provide in a micro-miniature relay an improved contact construction making for a more rugged assembly giving greater shock and vibration immunity.

Another object of the invention is to provide a microminiature relay wherein each component is cooperatively arranged to encompass an exceedingly simple construction adapted for commercial production at a reduced cost.

Other objects of the invention will become apparent from the following description and the accompanying drawings, in which:

Fig. 1 is a perspective view of the micro-miniature relay of the present invention;

Fig. 2 is an exploded view of the micro-miniature relay of the present invention considerably amplified, with the several components thereof being shown in cooperating electrical and physical relationship;

Fig. 3 is a plan view of the micro-miniature relay of the present invention with the casing in phantom and the insulator removed;

Fig. 4 is a transverse-cross sectional view of the microminiature relay taken along line 4-4 of Fig. 3;

Fig. 5 is a cross-sectional view of the invention taken along line 5--5 of Fig. 3; and

Fig. 6 is a perspective view, in detail, of the armature glass bead and actuator arm construction showing one actuator arm prior to fonning into a hook configuration represented by the other actuator arm.

Generally speaking of the present invention, it is a micro-miniature relay of the rotary armature type. A box or cavity type of construction is used; i.e., one block of space is used for the coils, a second block is allocated for the armature and a third block is allocated for the contacts. Formerly, the space present between the armature, per se, and the outer extremities of the relay was unused. The present construction provides an advance in miniaturization by utilizing this outer space by placing the contacts within the same space as the armature. As a result of this construction, the contact terminals are separable from the base terminal header, allowing for flexibility in the mounting of the relay in any type of terminal positioning. Furthermore, it gives complete independence from this base header and allows greater use in multiple package units since it reduces the overall volume of a multiplicity of relays within a small container. By placing the contacts within the armature cave ity, that space priorly allotted to the contacts, may be used for other purposes. Thus, in the present invention this space is used to obtain extra coil lengths providing greater sensitivity without an increase in the relay size, or conversely permitting asmaller relay size'for the present sensitivity of present type relays. The relay, in establishing the new construction, includes features of contact, armature and coil structure making for a ruggedness and simplicity enhancing the efficiency of the relay. In addition, the construction lends itself to commercial manufacture while providing for criticalness in assembly and maintaining the necessary precision requisite for such micro-miniature structures.

Referring now to the drawings, there is shown in Fig. l a micro-miniature relay generally indicated as 15. In use, there is a casing 16 which slips-over the relay and has an insulator flap 14 placed thereover so as to insulate the casing from the relay per se. The actual dimensions of the relay are x x 7 and-illustrate the ex treme necessity for criticalness in constructing the relay. In Fig. 2 the legends a=the center line for the coil. b=center line for the armature. c=center line for 2nd coil.

d=ground potential.

e= ground potential.

f= center line for electrical connection. g=center line for electrical connection. h=center line for electrical connection. j=e1ectrical connection.

k=electrical connection.

l=electrical connection.

The relay comprises a three piece U shaped magnet 17 including a base 18 and two legs 19 and 20. The base 18 has two apertures placed therethrough to accept an end portion 21 of each of the legs. Each leg comprises an end cylindrical portion 21 attached to a larger central cylindrical main section 22 and a hemispherical bottom tip portion 23. These bottom tip portions act as pole pieces and are constructed to passthrough co-operating hemispherical portions 24-27 formed in spring plates. As noted, there is formed a shoulder between the front cylindrical tip and the larger cylindrical portion. The flat top portion of the magnet will thus be able to be seated on the shoulders of the larger cylindrical portions of the legs. It is also to be noted that the bottom tips, acting as pole pieces, have their adjacent hemispherical faces reversed in direction.

The relay coils are wound on coil bobbins 30, 31. Each bobbin containing the coils, has a pair of flat-disclike bobbin ends 32 which are apertured to allow'the magnet legs to pass therethrough. A terminal 33 for each coil is provided at one of the bobbin discs. Also fastened to the legs of the magnet are a flat spring plate 34 and a U-shaped spring plate 35. One of the plates is flat and the other has downwardly extending flanges and two cut-out tongue portions 36, which will act as stops for the rotating armature 37. The spring plates also have the oppositely disposed semi-circular apertures cut through them so as to allow the plates to'slip over the face of the pole pieces. In this way, the legs of the magnet and the two spring plates form a box into which the armature may be placed and mounted on bearings for angular rotation.

Each of the plates, as seen, has a hole formed therein to accommodate the mounting portion of the bearings for the armature. Within the same cavity but between the ends of the armature and the outside dimensions of the relay, that is; between the side ends of the armatures and the relay casing, is placed the individual assemblies 38, 39. The contacts in the assembly or'header are so placed as to provide electrical clearance to the armature and to the outside covering for the relay, if used alone, or for an adjacent relay, ifincorporated in a multiple relay as- 4. sembly. The contact assemblies or headers, are placed on either side of the armature and substantially parallel to it. The stack ends 40, 41 for the contacts are placed to the outside of the pole pieces and are diagonal to one another (Fig. 4), opposite the striking surface of the armature.

As stated, the armature (Fig. 6) is a rotary type having a rectangular slab configuration. The armature is blanked out of soft iron magnetic steel material and two holes are pierced therethrough, one at each end thereof. Pieces of wire 43, 44 are placed in the holes and are embedded in glass beads 45, 46. The units are then fired whereby the glass is fused to the wire giving a tight glassmetal seal between the armature and wire. The wire is thus fixed into and is rigidly held in glass so as to form a strong mechanical bond and giving an excellent electrical insulation. The armature itself rotates on pair of cone shaped bearings, the pivot points thereof falling with holes formed in opposite sides thereof. The pivots are supported on the spring plates by having the bearings fit into co-operative holes formed in the spring plates.

Each of the two contact assemblies comprise a pair of flag-like stationary contacts 47, 48 placed on each side of a swinging contact arm 49. The base or the header is made of a jacket of suitable material having three apertures into which a glass head support having three apertures is placed. The bead has metal tubes inserted into the three apertures. The unit is placed into an oven and fired so that the glass fuses with the outside jackets and the beads providing an electrical insulation as well as a mechanical hold. The contact arms are then individually placed in each tube to be held rigidly thereby.

As noted, the swinging arm is adapted to be placed in a tube and is situated between the two flag shaped side fixed contact arms. The contact 50 itself may be integral with or be slipped on separately to the main shank portion of the swinging arm to a determined place thereon. In tests using various spacings, it was found that a contact spacing of .005.007 gave good results.

In operation, the relay has the two'coils energized to generatea flow in the magnet. The coils are wound with 2900 turns of epoxy coated wire and have a resistance of 850 ohms. The flux generated attracts the armature to the pole pieces in a rotary fashion. The armature finally comes to rest against the two pole pieces but on opposite sides of the magnets. Stops are also provided by the tongues stuck out of the bottom spring plate, as described. Since the hook-like actuating arms attached to the armature, are diagonally situated with reference to each other on that face of the armature which does not strike the pole pieces, they too will rotate. The actuating arms 60, 61 are formed from wires 43, 44 so that they engage the swingable contact arm at the free end 70 at a place above'the contact per se. The stationary contacts being substantially fixed at the opposite end in theheader will then be engaged and pivot and move in the same direction as the armature, thus breaking away from the outside contact 47 to engage the inner contact 48.

The present invention of a micro-miniature relay of a rotary armature type has provided an improved construction in which the electrical contacts are mounted within the same cavity as that of the armature; The contacts and armature are mounted within a box-like con' struction. This offers means for providing increased coil capacity and enhances the efiiciency and sensitivity of the relay for unit size. In the assembly, the mode of mounting of the contacts gives them increased stability by fixing the contact rods or arms within a rigid bond of glass. This forms an excellent mechanical bond and provides optimum electrical insulation within minimum of space. The invention by such constructional features, detailed above, permits the automated and commercial manufacture of an extremely critically dimensioned electrical device.

The forms and modification of the invention here described and illustrated are presented merely as examples of how the invention may be applied. Other forms, embodiments and applications of the invention will, of course, suggest themselves to those familiar with the electrical art.

What is claimed is:

1. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to a power source, a pair of spring plates connected to said legs, one of said plates being flat, the other of said plates having downward extending flanges and struck out separately extending tongues on opposite ends thereof, said plates being spaced from each other to define a spatial cavity, an armature rotatably mounted within said cavity, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including two fixed side contact bearing arms and a swingable contact bearing arm, contact arm engaging means placed at each end of said armature for engaging the swingable contact bearing arm, electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced angularly to rotate toward said magnet legs and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

2. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to a power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate having downwardly extending flanges and struck out tongues extending therefrom, said plates being spaced from each other to define a spatial cavity, an armature rotatably mounted within said cavity, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including two fixed side contacts and a swingable contact bearing arm, hook-shaped contact ar-m engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

3. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of epoxy coated wire wound on a bobbin placed on each leg, each coil connected to a suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate having downwardly extending flanges and struck out tongues extending therefrom, said plates being substantially spaced from each other todefine a spatial cavity, an armature rotatably mounted within said cavity on pivots, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, said swingable arm having a contact thereon and a free end, hookshaped contact arm engaging means placed at each end of said armature for engaging the swingable arm at the free end thereof, output electrical terminal means connected to said contact assembly at the sides of said armature will be induced to singularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

4. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to a suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate having downwardly extending flanges and struck out tongues extending therefrom, said plates being substantially spaced from each other to define a rectangular spatial cavity, an armature rotatably mounted within said cavity on pivots held by said plates, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed flag-shaped side contacts and a swingable contact bearing arm, each swingable arm having a contact thereon and a free end situated thereabove, contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to singularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

5. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to a power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate having downwardly extending flanges and struck out tongues extending therefrom, said plates being spaced from each other to define a spatial cavity, an armature rotatably mounted within said cavity, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder and having two fixed side contacts and a swingable contact bearing arm, hook-shaped contact arm engaging means placed in a glass bead at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said swingable arms of said side contact assemblies .to electrically control and switch circuits connected to said output terminals of said contact assemblies.

6. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate having downwardly extending flanges and struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet passing through said cavity to form magnetic pole pieces, an armature rotatably mounted within said cavity on pivots held by said plates, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm hook-shaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

7. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a fiat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates 'oeing flat, said other plate having downwardly extending flanges and struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet passing through said cavity to form magnetic pole pieces, an armature rotatably mounted within said cavity on pivots held by said plates, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed contacts and a swingable contact bearing arm, tubular means fixed in glass beads supporting said side contacts and said swingable contact bearing arm in said holder, hook-shaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

8. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate having a U-shape including downwardly extending flanges and struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, a supporting base header joined to said U-shaped plate, said legs of said magnet passing through said cavity to form magnetic pole pieces, an armature rotatably mounted within said cavity on pivots held by said plates, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, hook-shaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

9. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate being U-shaped and having downwardly extending flanges with struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet passing through said cavity to form magnetic pole pieces, an armature rotatably mounted and moveable toward said pole pieces within said cavity on pivots held by said plates, said tongues acting as opposing a stop for said armature, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, hook-shaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said M swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said con-tact assemblies.

10. A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate being U-shaped and having downwardly extending flanges with struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet having semi-circular portions passing through said cavity to form semi-circular magnetic pole pieces, an armature rotatably mounted and moveable toward said pole pieces within said cavity on pivots held by said plates, said tongues acting as opposing stops for said armature, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, hook-shaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminals of said contact assemblies.

11, A micro-miniature relay comprising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire Wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate being U-shaped and having downwardly extending flanges with struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet having semi-circular portions passing through said cavity to form semi-circular magnetic pole pieces, an armature rotatably mounted and moveable toward said pole pieces within said cavity on pivots held by said plates, said tongues acting as opposing stops for said armature when swinging away from said pole pieces, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, hook-shaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to angularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

12. A micro-miniature relay comprising 'a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate being U-shaped and having downwardly extending flanges with struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet passing through said cavity to form magnetic pole pieces, an armature rotatably mounted and moveable toward said pole pieces within said cavity on pivots held by said plates, said tongues acting as opposing stops for said armature when swinging away from said pole pieces, a base header connected to said U-shaped spring plate, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, hook-shaped contact arm engaging means placed at each end of said armature for engaging the 9 swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to singularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies.

13. A micro-miniature relay for use in multiple package units, said relay compnising a U-shaped magnet having a pair of legs dependent from a flat top portion, a coil of wire wound on a bobbin placed on each leg, each coil connected to suitable power source, a pair of spring plates connected to said legs, one of said plates being flat, said other plate being U-shaped and having downwardly extending flanges with struck out tongues extending therefrom, said plates being substantially spaced from each other to define a spatial cavity, said legs of said magnet passing through said cavity to form magnetic pole pieces, an armature rotatably mounted and moveable toward said pole pieces within said cavity on pivots held by said plates, said tongues acting as opposing stops for said armature when swinging away from said pole pieces, a base header connected to said U-shaped spring plate, contact assembly means placed at each side of said cavity adjacent the side ends of said armature, said assembly means including a holder having two fixed side contacts and a swingable contact bearing arm, hookshaped contact arm engaging means placed at each end of said armature for engaging the swingable arm of said assembly means, output electrical terminal means connected to said contact assembly at the sides of said armature, whereby upon said power source activating said coils, said armature will be induced to singularly move and to activate said swingable arms of said side contact assemblies to electrically control and switch circuits connected to said output terminals of said contact assemblies, a saving in the overall size of said multiple package unit being aflorded since the base header of the complete unit is separated from the contact header with each relay being brought closer together.

References Cited in the file of this patent UNITED STATES PATENTS 1,167,067 Hill Jan. 4, 1916 1,763,003 Mead June 10, 1930 2,767,279 Hall Oct. '16, 1956 2,824,189 Zimmer Feb. 18, 1958 

